Historically, automotive instrument panels are one of the longest lead time components to develop when manufacturing a new automobile body. Instrument panel development and tooling takes a great deal of time because of the typical complexity of the instrument panel case required to locate the gauges and provide the proper lighting. Lighting related problems directly result in case complexity and invariably result in much trial and error development work in order to uniformly light the instrument panel gauges, pointers and telltales.
In an effort to simplify the manufacture of automotive instrument panels, the assignee of the present invention developed an instrument panel utilizing a light distribution layer for illuminating the entire instrument panel with relatively few light sources. This instrument panel and related method of manufacture are shown in published PCT patent application No. WO 92/19992 having an international publication date of Nov. 12, 1992. This PCT application, as well as typical prior art instrument panels, illuminate analog gauge pointers by introducing light into the pointers using a light pipe (or light distribution layer) having a conical hole formed in the light pipe to direct light axially into the pointer.
Alternatively, a cylindrical hole is formed in the light pipe and a pointer boss projects into the light pipe cylindrical hole to pick up light. A problem associated with these types of pointer lighting systems is that they are relatively inefficient and frequently multiple light sources are needed to provide ample pointer lighting for each gauge.
In the conventional systems, since pointers are illuminated by the same light source or sources that illuminate the instrument panel graphic layer, the intensity of a pointer lighting cannot be varied independently of the graphic layer.
Other problems commonly facing instrument panel designers using the prior art techniques, is the design and placement of telltale lights. It is normally difficult to place telltales adjacent to an analog gauge. There is typically too much physical hardware associated with the gauge motor and associated light pipe to locate a telltale within the gauge scale in small meters such as fuel gauges or oil pressure gauges to display a low fuel or low oil pressure telltale within the analog gauge scale. Similarly, the illumination of telltales which are positioned adjacent other gauge indicia results in the telltale light source partially illuminating the adjacent scale indicia causing discoloration and non-uniformity in the indicia lighting.